Finite Element Modeling On Behaviour Of Reinforced Concrete Beam Column Joints Retrofitted With CFRP Sheets Using Ansys

T. Subramani et al. Int. Journal of Engineering Research and Applications www.ijera.com
ISSN : 2248-9622, Vol. 4, Issue 12( Part 5), December 2014, pp.69-76
www.ijera.com 69 | P a g e
Finite Element Modeling On Behaviour Of Reinforced Concrete
Beam Column Joints Retrofitted With CFRP Sheets Using Ansys
T. Subramani1
, S.Krishnan2
, M.S.Saravanan3
, Suboth Thomas4
1
Professor & Dean, Department Of Civil Engineering, VMKV Engineering College, Vinayaka Missions
University, Salem, India.
2
Associate Professor and Head, Department of Mechanical Engineering, Mahendra College of Engineering,
Salem, India.
3
Associate Professor, Department Of Civil Engineering, Annapoorana Engineering College, Salem, Tamilnadu,
India.
4
Professor & Director, Salem School of Architecture, Vinayaka Missions University, Salem, India.
ABSTRACT
Recent earthquakes have demonstrated that most of the reinforced concrete structures were severely
damaged during earthquakes and they need major repair works. Beam column joints, being the lateral and
vertical load resisting members in reinforced concrete structures a r e p a r t i c u l a r l y v u l n e r a b l e t o
f a i l u r e s d u r i n g e a r t h q u a k e s . The existing reinforced concrete beam column joints which are
not designed as per code IS13920:1993 must be strengthened since they do not meet the ductility
requirements. The Finite element method (FEM) has become a staple for predicting and simulating the
physical behaviour of complex engineering systems. The commercial finite element analysis
(FEA) programs have gained common acceptance among engineers in industry and researchers. The
details of the finite element analysis of beam column joints retrofitted with carbon fibre reinforced
polymer sheets (CFRP) carried out using the package ANSYS are presented in this paper. Three exterior
reinforced concrete beam column joint specimens were modelled using ANSYS package. The first specimen
is the control specimen. This had reinforcement as per code IS 456:2000. The second specimen which is also
the control specimen. This had reinforcement as per code IS 13920:1993. The third specimen had
reinforcement as per code IS 456:2000 and was retrofitted with carbon fibre reinforced polymer (CFRP)
sheets. During the analysis both the ends of column were hinged. Static load was applied at the free end of
the cantilever beam up to a controlled load. The performance of the retrofitted beam column joint was
compared with the control specimens and the results are presented in this paper.
KEYWORDS: Finite Element Modelling, Behaviour, RCC Beam Column Joints Retrofitted With CFRP
Sheets, Ansys
I INTRODUCTION
The techniques of using fiber sheets for
strengthen the beam-column joints have a
number of favourable characteristics such as ease
to install, immunity to corrosion and high
strength. The simplest way to strengthen the joints
is to wrap fibres sheets in the joint region in two
orthogonal directions. Many fibre reinforced
polymer sheets are available in the market for
strengthening reinforced concrete members.
Carbon fibre reinforced polymer sheets are
commonly used for retrofitting the structural
elements. During the present investigation,
ANSYS modelling of reinforced concrete
beam-column joints has been carried out to
understand the behaviour of retrofitted reinforced
concrete beam-Column joint specimens retrofitted
with carbon fibre wrapping sheets.
II INTRODUCTION TO ANSYS
The ANSYS program has many finite
element analysis capabilities, ranging from a simple,
linear, static analysis to a complex non – linear,
transient dynamic analysis.
A typical ANSYS analysis has three distinct steps:
 Building the model
 Applying loads and obtains the
solution
 Review the results.
2.1 BUILDING THE MODEL:
Building a finite element model requires a
more of an ANSYS user’s time than any other part
of the analysis. First you specify the job name and
analysis title. Then, define the element types, real
constants, and material properties, and the model
geometry.
2.2 DEFINING ELEMENT TYPES:
RESEARCH ARTICLE OPEN ACCESS

The analysis element library contains more
than 100 different element types. Each element type
has a unique number and a prefix that identifies the
element category. Example: beam, pipe, plant, shell,
solid.
2.3 DEFINING ELEMENT REAL CONSTANTS:
Element real constant are the properties that
depend on the element type, such as cross sectional
properties of a beam element. For example real
constants for BEAM3 , the 2-d beam element, or
area, moment of inertia(IZZ), height , shear
deflection constant (SHEAR Z), initial strain
(ISTRN) different elements of same type may have
different real constant values.
2.4 DEFINING MATERIAL PROPERTIES:
Most elements types require material
properties. Depending on the application, material
properties may be:
 Linear or non linear
 Isotropic, Orthotropic, or an isotropic
 Constant temperature or temperature –
dependant
As with element type and real constant, each
set of material properties has a material reference
number. The table of material reference number
verses material property set ids called material
property table. Within, one analysis you may have
multiple material properties set.
2.5 MATERIAL PROPERTY TEST:
Although you can define material properties
separately for each element analysis, the ANSY
program enables you to store a material property set
in an archival material library file, then retrieve the
set and reuse it in multiple analysis. The material
library files also enable several ANSYS user to share
common used material property data.
III OVERVIEW OF MODEL
GENERATION
The ultimate purpose of finite element
analysis which to recreate mathematical the
behaviour of an actual engineering system. In other
words, the analysis must be an accurate
mathematical model of a physical prototype. In the
broadest sense, this model comprises all the nodes,
elements, material properties, real constant,
boundary conditions, and other features that are used
to represent the physical system. In ANSYS
terminology, the term model generation usually
takes on the narrower meaning of generating the
nodes and elements that represent the spatial volume
and connectivity of actual system. Thus, model
generation in this discussion will mean the process
of define the geometric configuration model’s nodes
and elements.
The ANSYS program offers you the following
approaches to model generation:
 Creating a solid model within
ANSYS.
 Using direct generation reporting a
model created in CAD system.
3.1 MESHING YOUR SOLID MODEL:
The procedure for generating a mesh of
nodes & elements consists of three main steps:
 Set the element attributes
 Set mesh controls
 Generate the mesh controls,
The second step, setting mesh
controls, is not always necessary because the default
mesh controls are appropriate for many models. If
no controls are specified, the program will use the
default setting on the de size command to produce a
free mesh. As an alternative, you can use the small
size feature to produce a better quality free mesh.
3.2 FREE ARE MAPPED MESH:
Before meshing the model, and even before
building the model, it is important to think about
whether a free mesh or a mapped mesh is
appropriate for the analysis. A free mesh has no
restrictions in terms of element shapes, and has no
specified pattern applied to it.
Compared to a free mesh, a mapped mesh
is restricted in terms of the element shape it contains
and the pattern of the mesh. A mapped area mesh
contains either only quadrilateral or only triangular
elements, while a mapped volume mesh contains
only hexahedron elements. In addition, a mapped
mesh typically has a regular pattern, with obvious
rows of elements. If you want this type of mesh,
you must build the geometry as series of fairly
regular volumes and or areas that can accept a
mapped mesh.
3.3 SETTING ELEMENT ATTRIBUTES:
Before you generate a mesh of nodes and
elements, you must first define the appropriate
element attributes. That is, you must specify the
following:
 Element type
 Real constant set
 Material properties set
 Element co-ordinate system.
LOADING:
The main goal of finite element analysis is
to examine how a structure or component response
to certain loading condition. Specifying the proper
loading conditions, therefore, a key stepping
analysis. You can apply loads on the model in
variety of ways in ANSYS program.
LOADS:
The word loads in ANSYS terminology includes
boundary.

Conditions and externally or internally applied
forcing functions. Example of loads in different
disciplines is: Structural: displacement, forces,
pressures, temperatures (for thermal strain), gravity
Thermal: temperatures, heat flow rate, convections,
and internal heat generation, infinite surface
Magnetic: Magnetic Potentials, magnetic flux, and
magnetic current segment
Electric: electric potentials, electric current, charges,
charge densities, infinite
Fluid: Velocities and pressures
A DOF constraint fixes the degrees of
freedom of a known value. Examples of constraints
are specified displacement and symmetric boundary
conditions in structural analysis, prescribed
temperatures in thermal analysis, and flux parallel
boundary conditions.
A force is concentrated load applied at a
node in a model. Examples are forces and moments
in structural analysis, heat flow rates in thermal
analysis.
A surface load is distributed load applied over a
surface. Examples are pressures in structural
analysis and convections and heat fluxes in
thermal analysis.
Coupled field loads are simple case of one
of the above loads, where results from analysis are
used as loads in another analysis. For examples you
may apply magnetic forces calculated in magnetic
field analysis are force loads in structural analysis.
3.4 HOW TO APPLY LOADS:
You can apply loads most loads either on the
solid model (on key points, line, areas) or on the
finite element model (on nodes and elements). For
example, you can specify forces at a key point or a
node. Similarly, you can specify convections (and
other surface loads) on lines and areas or nodes and
element faces.
No matter how you specify loads, the solver
expects all loads to be in term of finite element
model. Therefore if your specify loads on the solid
model, the program automatically transfers them to
the nodes and element at the beginning of the
solution.
3.5 SOLUTION:
In the solution phase of the analysis, the
computer takes over and solves the simultaneous
equations that the finite element method generates.
The result
Solution is: a nodal degree of freedom value, which
form the primary solution, and b) derived values,
which form the element solution. The element
solution is usually calculated at the elements
integration points. The ANSYS program writes the
results to the database as well as to the result file.
(Job name. rst , rth, rmg, or. rfl}.
Several methods of solving the simultaneous
equations are available in the ANSYS program:
frontal solution, sparse direct solution, Jacobi
Conjugate gradient (JCG solution, incomplete
cholesky conjugate (ICCG) solution, preconditioned
conjugate gradient (PCG) solution, automatic
iterative solver option (ITER). The frontal solver is
the default, but you can select a different solver.
3.6 POST PROCESSING:
After building the model and obtaining the
solution, you will want answers to some critical
question: will the design really work when put to
use? How high are the stresses in this region? How
does the temperature of this part vary with time?
What is the heat loss across my model? How does
the magnetic flow through this device? How does
the placement of this object affect fluid flow? The
post processors in the ANSYS program can help you
find answer these questions and others. Post
processing means reviewing the results of an
analysis. it is probably the most important step in
the analysis, because you are trying to understand
how the applied loads affect your design, how good
you finite element mesh is, and so on.
Two post processors are available review
your results: Post 1, the general post processor, and
post 26, the time history post processor. Post 1
allows you to review the results over the entire
model at specific load steps and sub steps (or at
specific time – points or frequencies). In a static
structural analysis, for example, you can display the
stress distribution for load step 3 or, in a transient
thermal analysis; you can display the temperature
distribution at time – 100 seconds.
3.7 THE RESULT FILES
The ANSYS solver writes results of an
analysis to the results file during solution. The name
of the results file depends on the analysis discipline:
Job Name. rst for structural analysis.
3.8THE GENERAL POST PROCESSOR
You use Post1, the general post processor,
to review analysis results over the entire model, or
selected portion of the model, of a specifically
defined combination of loads at a single time (or
frequency). Post 1 has many capabilities, ranging
from simple graphics display and tabular listing to
more complex data manipulation such as load case
combinations.
DISPLAYING RESULTS GRAPHICALLY:
Graphics display is perhaps the most
effective way to review results. You can display the
following types of graphics in post1:
 Contour displays
 Deformed shape displays
 Vector displays
 Path plots
 Reaction force displays
 Particle flow traces.

IV INTRODUCTION TO STRUCTURAL
ANALYSIS
Structural analysis is probably the most
common application of the finite element method.
The term structural (or structure) implies not only
civil engineering structures such as bridges and
buildings, but also naval, aeronautical and
mechanical structures such as ship hulls, aircraft
bodies and machine housings, as well as mechanical
components such as pistons, machine parts and
tools.
Types of structural analysis.
The seven types of structural analysis
provided by ANSYS are given below.
1. Static analysis: used to determine
displacement, stresses etc. under static
loading conditions. Both linear and non-
linear static analyses. Non – Linearity’s
can include plasticity, stress stiffening,
large deflection, large strain, hyper
elasticity, contact surfaces, and creep.
2. Modal analysis: used to calculate the
natural frequencies and mode shapes of a
structure. Different mode extraction
methods are available.
3. Harmonic analysis: used to determine the
response of a structure to harmonically
time varying loads.
4. Transient dynamic analysis: used to
determine the response of a structure to
arbitrarily time varying loads. All non-
linearity’s mentioned under static analysis
above are allowed.
5. Spectrum analysis: an extension of the
model analysis, used to calculate stress
and strain due to response spectrum or a
PSD input (random vibrations).
6. Buckling analysis: used to calculate the
buckling load and determine the buckling
mode shape. Both linear (eigenvalue)
buckling and non –linear buckling
analyses are possible.
7. Explicit dynamic analysis – ANSYS
provides an interface to the LS-
Dynamic explicit finite element programs is
used to calculate fast solution for large
deformation dynamics and complex contact
problems.
V MODELING
The beam column joint considered for
analysis consists of a cantilever portion and
column portion as shown in Figure 1.a and Figure
1.b. The column had a cross section of200 mm x 200
mm with an overall length of 1500 mm and the
beam had a cross section of 200 mm x 200 mm and
the length of the cantilevered portion was 600 mm.
The control
Specimens were designated as C1 and C2. C1 had
reinforcement as per code IS 456-2000 And C2 had
reinforcement as per code IS 13920-1993. The
specimen retrofitted with Carbon reinforced
polymer sheet was designated as C3 which had
reinforcement as per code IS 456-2000. The column
portion was reinforced with 4 numbers of 12mm
diameter Fe 415 rods and the beam portion was
reinforced with 2 numbers of 16 mm diameter Fe415
rods each in the tension and compression zones. The
lateral ties in the columns of the specimens C1 and
C3 were 6 mm diameter Fe 250 bars with the
spacing of 180 mm c/c as per code IS 456:2000,
clause 26.5.3.2(c). Beam had vertical stirrups of 6
mm diameter Fe 250 bar at 120 mm c/c as per
code IS 456:2000, clause 26.5.1.6. The
development length of the tension and compression
rods in beam were also provided as per
clause26.2.1 of code IS 456:2000. For the specimen
C2, the lateral ties in the columns consisted of 8 mm
diameter Fe 415 bar at 75 mm c/c for the central
distance of 1100 mm as per code IS 13920:1993,
clause 7.4.6 and 6mm diameter Fe250 bars at 100
mm c/c for the remaining length of the column.
Beams had vertical stirrups of 6 mm diameter Fe 250
bar at 40 mm c/c. up to a distance of 340 mm from
the face of the column as per code IS13920:1993,
clause 6.3.5 and 6 mm diameter Fe250 bar at 80
mm c/c for remaining length of the beam.
Figure 5.1.Typical View of ANSYS Model
Detailed as per code IS 456:2000

Figure 5.2.Typical View of ANSYS Model
Detailed as per code IS 13920:1993
The development length of the beam rods were also
provided as per code IS 13920:1993, clause 6.2.5.
M20 grade of concrete was adopted. The typical
views of the ANSYS model of the specimens are
shown in Figure.5.1 and Figure.5.2 Meshing was
done for both control and retrofitted specimens using
ANSYS. Both ends of the column were hinged.
The concrete was modelled using Solid 65
element. The reinforcement was modelled using
Link 8 element. The wrapping was modelled
using Solid 45 element. The static load was applied
at the free end of the cantilever beam at a regular
load interval of 5 kN for the control and
retrofitted reinforced concrete beam- column joint
models. The performance of the retrofitted
beam-column joint specimen was compared with the
control beam-column joint specimens. Figure.5.3 and
Figure. 5.4 show the meshing for the control and
retrofitted specimen.
Figure 5.3: Typical meshed
Control Specimen
Figure.5.4 Typical meshed
Retrofitted specimen
VI NON LINEAR MODELLING OF THE
BEAM COLUMN JOINTS
Non–linear a na l ys i s wa s done f o r t hr ee
beam column speci me ns using the software
ANSYS. A transverse static was applied at the free
end of the beam to develop a bending moment at
the joint. The load was increased in steps till a
controlled load of 20 kN. The deflection at the
free end of the cantilever beam was noted. The
deflections of the specimen C1 were found to be
3.5 mm for the load of 5 kN, 5 mm for the load of
10 kN, 15.5 mm for the load of 15 kN and
42.5 mm for the load of 20 kN. The same

procedure was repeated for the specimen detailed
as per code IS 13920-1993 and for the retrofitted
specimen. .
Table 6.1 Deflections of Control and Retrofitted
Specimens.
Specimen Deflection in mm for the load of
5 kN 10 kN 15 kN 20 kN
C1 3.5 5.0 15.5 42.5
C2 2.5 3.5 10.0 32.5
C3 1.0 2.0 8.0 10.5
Table 6.2 Comparison between Deflection and
Energy Absorption Capacity
Specimen
I
D
Def. in
mm for the
loa
d
of
20
kN
%
reduction
in
deflection
E.A.C up to
a
def. of 10
mm
% increase
in E.A.C
C
1
4
2
.
5
-
-
61.25
kN.mm
-
-
C
2
3
2
.
5
23.53 87.50
kN.mm
42.86
C
3
1
0
.
5
75.29 131.25
kN.mm
114.89
Figure 6.1 Typical View of Deflected
Control Specimen (IS 456-2000)
Figure 6.1, Figure 6.2, and Figure 6.3 show the
typical views of the deflected control and retrofitted
specimens. Figure 6.4. shows the load deflection
curve for the control and retrofitted specimens. Table
6.1.shows the deflections at various interval Of load
of the control and retrofitted specimens. Table.6.2
shows comparison between the Deflections and
energy absorption capacity of the control and
retrofitted specimens.
Figure 6.2 Typical View of Deflected Control
Specimen (IS 13920-1993)
Figure 6.3 Typical View of Deflected Retrofitted
Specimen

Figure 6.4. Load Deflection Curve for the Control
and Retrofitted Specimen
VII DISCUSSION OF THE RESULTS
It can be found from the Table 2. that
the deflection of the beam-column joint
specimen detailed as per code IS 13920-1993 is
23.53 % less than that of the specimen detailed
as per code IS 456-2000 and deflection of the
beam-column joint specimen retrofitted with
carbon reinforced polymer sheet was 75.29 %
less than that of the specimen detailed as per
code IS 456-2000.The energy absorption
capacity of the specimen beam-column joint
specimen detailed as per code IS 13920-1993 is
42.86 % more than that of the specimen detailed
as per code IS 456-2000 and energy absorption
capacity of the beam-column joint specimen
retrofitted with carbon reinforced polymer sheet
was 114.29 % more than that of the specimen
detailed as per code IS 456-2000.
VIII CONCLUSIONS
Based on the ANSYS modeling and
analysis carried out on the control and
retrofitted beam-column joint specimens using
CFRP sheets, the following conclusions were
drawn.
 The deflection of the beam-column joint
specimen detailed as per code
IS13920-1993 was found to be 23.53 % lower
than that of the specimen detailed per code IS
456-2000.
 The deflection of the beam-column joint
specimen retrofitted with GFRP sheet reduced
the deflection about 75.29 %.when
compared with the deflection of specimen
detailed as per code IS 456-2000.
 The energy absorption capacity of the
beam-column joint specimen detailed as per
code IS 13920-1993 was found to be 42.89
% higher than that of the specimen detailed
per code IS 456-2000.
 The energy absorption capacity of the
beam-column joint specimen retrofitted with
CFRP sheet increased about 114.29 %.when
compared with the energy absorption capacity
of specimen detailed as per code IS 456-2000.
REFERENCES
[1]. Bindu K.R.,Jaya K.P ., 2008. Performance
of Exterior Beam Column Joints with Cross
Inclined Bars Under Seismic Type Loading.
Journal of engineering and applied science.
vol.7,pp 591-597
[2]. Alexander G. Tsonos ., 2008. Effectiveness
of CFRP Jackets and RC Jackets in Post
Earthquake and Pre Earthquake Retrofitting
of Beam Column Sub Assemblages, Journal
of engineering structures vol. 30,pp 777-793.
[3]. Lakshmi G.A, Anjan Dutta, Deb S.K
Grim, R.E., 2008. Numerical Study of
Strengthening of Beam Column Joints
Under Cyclic Excitation Using FRP
Composites, Journal of structural
engineering, vol 35,pp 59-65.
[4]. Yousef A. Al-Salloum , Tarek
H.Almusallam , 2007. Seismic Response
of Interior RC Beam Column Joints
Upgrade with FRP Sheets. I: Experimental
Study Journal of composite for construction
vol. 11,pp 575-589.
[5]. Yousef A. Al-Salloum , Tarek
H.Almusallam , 2007. Seismic Response
of Interior RC Beam Column Joints
Upgrade with FRP Sheets. II: Analysis
And Parametric Study , Journal of composite
for construction vol. 11,pp 590-599.
[6]. Devados Menon ,Pradip Sarkar , Rajesh
Agrawal , 2007, Design of RC Beam
Column Joints Under Seismic Loading
– A Review , Journal of structural
engineering, vol. 33,pp 449-457.
[7]. Subramani,T , Athulya Sugathan, “Finite
Element Analysis of Thin Walled- Shell
Structures by ANSYS and LS-DYNA”,
International Journal of Modern Engineering
Research,Vol.2, No.4, pp 1576-1587,2012.
[8]. Subramani.T , Senthil Kumar.R, “Modelling
and Analysis of Hybrid Composite Joint
Using Fem in ANSYS”, International
Journal of Modern Engineering Research,
Volume 4, Issue 6 (Version 1), pp 41- 46,
2014.
[9]. Subramani.T, Manivannan.R, Kavitha.M,
"Crack Identification In Reinforced Concrete

Beams Using Ansys Software" ,International
Journal of Engineering Research and
Applications, Volume. 4, Issue. 6 (Version
6), pp 133 - 141, 2014.
[10]. Subramani.T, Subramani.M, Prasath.K,"
Analysis Of Three Dimensional Horizontal
Reinforced Concrete Curved Beam Using
Ansys" International Journal of Engineering
Research and Applications, Volume. 4,
Issue. 6 (Version 6), pp 156 - 161, 2014.

Finite Element Modeling On Behaviour Of Reinforced Concrete Beam Column Joints Retrofitted With CFRP Sheets Using Ansys

More Related Content

What's hot

Viewers also liked

Similar to Finite Element Modeling On Behaviour Of Reinforced Concrete Beam Column Joints Retrofitted With CFRP Sheets Using Ansys

Recently uploaded

Finite Element Modeling On Behaviour Of Reinforced Concrete Beam Column Joints Retrofitted With CFRP Sheets Using Ansys